Modular battery system and a method of operating thereof

Abstract

A modular battery system and a method for providing an adjustable direct current (DC) voltage output. A precharge unit is provided which has a precharge contactor and a precharge resistor, the precharge resistor being configured such that its electrical resistance is increased as its temperature increases. The precharge unit includes an optocoupler arranged to detect a voltage difference across the precharge resistor.

1 . A modular battery system for providing an adjustable direct current (DC) voltage output, the modular battery system comprises:
 a precharge unit having a precharge contactor and a precharge resistor,   the precharge resistor being configured such that its electrical resistance is increased as its temperature increases, and   wherein the precharge unit comprises an optocoupler arranged to detect a voltage difference across the precharge resistor.   
     
     
         2 . The modular battery system of  claim 1 , wherein the optocoupler is configured to detect whether a voltage difference threshold value has been exceeded where a preliminary mode of precharging using the precharge unit during a power up procedure is considered successful. 
     
     
         3 . The modular battery system of  claim 1 , wherein the modular battery system is configured to stop precharging by operating the precharge contactor based on light emitted by a light emitter of the optocoupler. 
     
     
         4 . The modular battery system of  claim 3 , wherein:
 the modular battery system further comprises a photosensor configured to monitor light emitted by the optocoupler, and   the modular battery system is configured to stop precharging based on the photosensor no longer detecting light from the light emitter of the optocoupler.   
     
     
         5 . The modular battery system according to  claim 1 , wherein the optocoupler is arranged in a circuit parallel to the precharge resistor. 
     
     
         6 . The modular battery system according to  claim 5 , wherein the circuit is configured to guarantee that an electrical current through the optocoupler is less than or equal to a predetermined threshold value during precharging. 
     
     
         7 . The modular battery system according to  claim 5 , wherein the circuit comprises a first resistor (R 1 ), a second resistor (R 2 ) and a Zener diode arranged to limit electrical current through the optocoupler for predefined voltage differences across the precharge resistor. 
     
     
         8 . The modular battery system according to  claim 7 , wherein:
 the circuit has a first line connected to a first node between the precharge contactor and the precharge resistor, and a second line connected to a second node between the precharge resistor and an output of the modular battery system, the output connectable to an electrical load,   the first line is connected to the first resistor (R 1 ), the first resistor (R 1 ) being connected to the second resistor (R 2 ),   the second resistor (R 2 ) being connected to an anode of the optocoupler,   the second line is connected to a cathode of the optocoupler,   the Zener diode is arranged in a line connecting the second line to an intermediate node between the first resistor (R 1 ) and the second resistor (R 2 ), and   a cathode of the Zener diode is connected to the intermediate node.   
     
     
         9 . The modular battery system according to  claim 8 , wherein:
 the modular battery system comprises an auxiliary circuit having a same configuration as the circuit,   an auxiliary first line of the auxiliary circuit is connected to the second node between the precharge resistor and the output of the modular battery system, and   an auxiliary second line of the auxiliary circuit is connected to the first node between the precharge contactor and the precharge resistor.   
     
     
         10 . The modular battery system according to  claim 3 , wherein:
 the modular battery system includes a main contactor switchable between:
 a closed state, in which an energy storage unit of the modular battery system is electrically connected to an output, and 
 an open state, in which the electrical connection between the energy storage unit and the output is interrupted by the main contactor, 
   during precharging the main contactor is in the open state, and   the main contactor is switched to the closed state and the precharge contactor is opened in order to stop a preliminary mode of precharging based on light emitted by the optocoupler.   
     
     
         11 . The modular battery system according to  claim 1 , wherein the precharge resistor is a positive temperature coefficient (PTC) resistor. 
     
     
         12 . The modular battery system according to  claim 1 , wherein:
 the modular battery system has a concatenation of a number of battery modules,   each battery module including at least one rechargeable battery cell, and   the number of battery modules in the modular battery system and/or an arrangement of the battery modules in the modular battery system are adaptable.   
     
     
         13 . A method of performing a preliminary mode of precharging during a power up procedure of a modular battery system, the modular battery system configured to provide an adjustable direct current (DC) voltage output, wherein the method includes:
 providing a precharge unit including a precharge contactor and a precharge resistor, the precharge resistor being configured such that its electrical resistance is increased as its temperature increases, and   providing the precharge unit with an optocoupler for detecting a voltage difference across the precharge resistor.   
     
     
         14 . An electrical system or device including at least one modular battery system according to  claim 1 .